The black, green and gold were placed into Pool 1 alongside the Irish giants, who lost to Saracens in last season's showpiece, Lyon and Benetton Rugby.
Saints had a tough time the last time they faced Leinster in the pool stages, losing 37-10 at Franklin's Gardens in December 2016 before being thrashed 60-13 in the return game at the Aviva Stadium eight days later.But three years previously they had stunned Leinster at the same stadium, winning 18-9 as Jamie Elliott's late score put the seal on an incredible away success.
Lyon will provide intriguing new opposition for Saints, but they possess plenty of talent, having finished third in the French Top 14 last season, behind eventual champions Toulouse and Saints' familiar foes, Clermont Auvergne.
Benetton are an improving Italian side who finished third of seven in Guinness Pro14 Conference B last season, winning 11 of their 21 matches.Champions Cup pool drawPool 1: Leinster, Lyon, Saints, Benetton. Pool 2: Exeter, Glasgow, La Rochelle, Sale Sharks. Pool 3: Clermont, Ulster, Quins, Bath. Pool 4: Saracens, Munster, Racing 92, Ospreys. Pool 5: Toulouse, Gloucester, Connacht, Montpellier.
EPCR weekendsRound 1: November 15/16/17, 2019Round 2: November 22/23/24, 2019Round 3: December 6/7/8, 2019Round 4: December 13/14/15, 2019Round 5: January 10/11/12, 2020Round 6: January 17/18/19, 2020Quarter-finals: April 3/4/5, 2020Semi-finals: May 1/2/3, 2020Final: Saturday, May 23, 2020 (Marseille)